Camera does not work on my iPhone4

Hi,
It is an Apple iPhone 4 with 16 GB memory. Everything is okay. Sound, Internet browsing, SMS email etc. all are fine. But one thing is giving me pain for a week. My camera does not work. When I try to take a picture, some green and pink lines appear on the screen.
This is a second hand phone, and I have no warranty card, so that I can go to customer support center of iPhone.
It is bad luck for me that I bought it second hand.
I tried my best to repair, but it is not working. Now if I want to repair it, I must pay service charge. But I think, if anyone can advice me without cost, it will be better.
This is the screenshot:
